why does NSManagedObjectContext Queue execute on main thread?

Question

When I send a performBlock message to my MOC of type NSPrivateQueueConcurrencyType, like this:

[self.privateManagedObjectContext pe         


        

Answer 1

This optimization is possible because performBlockAndWait: executes the block synchronously, i.e. the method does not return until the block has finished. Therefore the block will not be executed in parallel with other operations on the main thread.

(For the same reason, dispatch_sync(queue, ...) may execute a block on the main thread instead of a separate thread.)